System for detecting catheter electrodes entering into and exiting from an introducer

ABSTRACT

Systems for detecting when catheter electrodes enter into and exit from an introducer are disclosed. In one form, a system detects a relative position of a catheter (comprising a marker band and an electrode) and an introducer (comprising a proximity sensor adapted to sense the marker band), while the catheter and introducer are in a human body. The system may comprise an electronic control unit to analyze signals from the catheter and/or the introducer, to determine whether the catheter electrode is within the introducer; and to disregard data collected from the electrode when that electrode is in the introducer. The sensor may be on the catheter and the sensed element may be on the introducer. The sensed element may comprise one or several marker bands. A marker band may be applied during the manufacture of a medical device or during its use and is any element capable of electromagnetic detection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/609,534, filed 31 May 2017 (the '534 application), which is acontinuation of U.S. application Ser. No. 13/839,963, filed 15 Mar. 2013(the '963 application), now U.S. Pat. No. 9,693,820. The '534application and the '963 application are both hereby incorporated byreference as though fully set forth herein.

BACKGROUND OF THE INVENTION a. Field of the Invention

This invention relates to systems, apparatuses and methods fornavigating a medical device within a body. In particular, the instantinvention relates to systems, apparatuses and methods for detecting whenone or more electrodes on a medical device enter into and/or exit froman introducer or other enveloping device while navigating the medicaldevice within a body.

b. Background Art

Electrophysiology catheters are used in a variety of diagnostic,therapeutic, and/or mapping and ablative procedures to diagnose and/orcorrect conditions such as atrial arrhythmias, including for example,ectopic atrial tachycardia, atrial fibrillation, and atrial flutter.Arrhythmias can create a variety of conditions including irregular heartrates, loss of synchronous atrioventricular contractions and stasis ofblood flow in a chamber of a heart which can lead to a variety ofsymptomatic and asymptomatic ailments and even death.

Typically, a catheter is deployed and manipulated through a patient'svasculature to the intended site, for example, a site within a patient'sheart. The catheter carries one or more electrodes that can be used forcardiac mapping or diagnosis, ablation and/or other therapy deliverymodes, or both, for example. Once at the intended site, treatment caninclude, for example, radio frequency (RF) ablation, cryoablation, laserablation, chemical ablation, high-intensity focused ultrasound-basedablation, microwave ablation, and/or other ablation treatments. Thecatheter imparts ablative energy to cardiac tissue to create one or morelesions in the cardiac tissue. This lesion disrupts undesirable cardiacactivation pathways and thereby limits, corrals, or prevents errantconduction signals that can form the basis for arrhythmias.

To position a catheter at a desired site within the body, some type ofnavigation may be used, such as using mechanical steering featuresincorporated into the catheter (or an introducer). In some examples,medical personnel may manually manipulate and/or operate the catheterusing the mechanical steering features.

In order to facilitate the advancement of catheters through a patient'svasculature, a navigating system may be used. Such navigating systemsmay include, for example, electric-field-based positioning andnavigating systems that are able to determine the position andorientation of the catheter (and similar devices) within the body. Insuch electric-field-based positioning and navigating systems, it can beimportant to know when the electrodes on the catheter are shieldedinside of a sheath or introducer that is being used to deliver thecatheter to a desired location.

The foregoing discussion is intended only to illustrate the presentfield and should not be taken as a disavowal of claim scope.

BRIEF SUMMARY OF THE INVENTION

The present disclosure generally relates to detecting when catheterelectrodes enter into, and/or exit from, an introducer or otherenveloping device in order to avoid, for example, introducingundesirable shift or drift into the determined catheter position andorientation based upon readings obtained by an electric-field-basedpositioning system.

In an embodiment, a system detects a relative position of a catheter andan introducer while the catheter and the introducer are in a human body,wherein the catheter comprises a marker band and an electrode and theintroducer comprises a proximity sensor adapted to sense the markerband. The system comprising (a) an electric-field-based positioningsystem; and (b) an electronic control unit electrically coupled to theelectric-field-based positioning system. The electronic control unit isoperable to do the following: (A) drive currents through a plurality ofpatch electrodes on a surface of the body and measure a resultingvoltage from the catheter electrode; (B) monitor a first signaloriginating from the proximity sensor to determine when the marker bandpass the proximity sensor; (C) analyze the first signal to determinewhether the catheter electrode is within the introducer; and (D)disregard the measured resulting voltage if the catheter electrode iswithin the introducer. In some embodiments, when the system disregardsmeasured resulting voltage data, it also communicates that fact to aclinician (e.g., by sending a message to a display or activating a lighton the catheter or the introducer.

In another embodiment, a system detects when a sensed element on a firstmedical device enter into or exist from an introducer, and the systemcomprises the following: (a) a first storage operable to store (i) firstlocation data relating to a location of the sensed element on the firstmedical device and (ii) second location data relating to a location of asensor on the introducer; (b) a second storage operable to store currentposition and orientation data relating to the first medical device; (c)a device operable to determine a relative position of the sensor and thesensed element based upon the stored first and second location data; and(d) a processor in communication with the first storage, the secondstorage, and the device. Further, in this embodiment, the processor isoperable to do the following: (1) consider the relative position of thesensor and the sensed element; (2) determine whether to disregard thecurrent position and orientation data for the first medical device; and(3) output a signal indicative of whether the current position andorientation data for the first medical device is being disregarded.

In yet another embodiment, a system detects when one or more catheterelectrodes enter into or exist from an introducer, and the systemcomprises the following: (a) an introducer comprising (i) an introducerproximal end, (ii) an introducer distal end, (iii) alongitudinally-extending introducer body extending between theintroducer proximal end and the introducer distal end; and (iv) a firstelement affixed to the introducer body; and (b) a catheter comprising(i) a catheter proximal end, (ii) a catheter distal end, (iii) alongitudinally-extending catheter body extending between the catheterproximal end and the catheter distal end; (iv) a plurality of electrodeson the catheter body; and (v) a second element affixed to the catheterbody and operable to electromagnetically interact with the firstelement. In one offshoot of this embodiment, the first element is aproximity sensor and the second element is a marker band on an outersurface of the catheter body. And, in another embodiment, the cathetercomprising part of the system may further comprise an indicator lightconfigured to report when at least one of the plurality of catheterelectrodes is located within the introducer.

In another embodiment, a catheter is provided that includes a shafthaving one or more electrodes at a distal portion of the shaft, andincludes a detectable marker positioned proximal to the one or moreelectrodes at the distal portion of the shaft. The detectable marker ispositioned at a predetermined distance from a most proximal one of theone or more electrodes. In a more particular embodiment of such acatheter, the predetermined distance may correspond to a distance from adistal opening of an interoperable introducer to a marker detectorpositioned along the introducer proximal to the distal opening. In stillanother particular embodiment of such a catheter, one or more additionaldetectable markers may each be positioned proximal to a plurality of theelectrodes at the distal portion of the shaft, where each of thedetectable markers is positioned a predetermined distance from arespective one of the plurality the electrodes.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is diagrammatic view of one embodiment of a system for navigatinga medical device within a body.

FIG. 2 depicts a steerable introducer having a sensor affixed to itsproximal end.

FIG. 3 depicts a fixed-curve introducer having a sensor detachablyconnected to its proximal end.

FIG. 4 is an isometric view of a detachable sensor.

FIG. 5 depicts an ablation catheter having a marker band on its shaftand on-board information storage in its handle.

FIG. 6 depicts a catheter assembly comprising the catheter of FIG. 5inserted through the steerable introducer of FIG. 2 .

FIG. 7 is an enlarged view of the circled region of FIG. 6 , depicting amost-proximal catheter electrode adjacent to the distal end of theintroducer shaft.

FIGS. 8 and 9 schematically depict the catheter and introducer depictedin, for example, FIGS. 2, 5, and 6 , and demonstrate how a change in thelocation of the marker band relative to the sensor corresponds to achange in the position of the most-proximal catheter electrode relativeto the distal end of the introducer.

FIG. 10 is similar to FIG. 6 , but depicts an assembly where thecatheter comprises multiple marker bands on the proximal portion of thecatheter shaft and multiple indicator lights on the catheter handlehousing.

FIG. 11 is similar to FIGS. 8 and 9 , but schematically depicts theintroducer and catheter shown in FIG. 10 , wherein the cathetercomprises a separate marker band for each electrode.

FIG. 12 is similar to FIGS. 6 and 10 , but depicts a catheter having aplurality of marker bands at a more distal location on the cathetershaft than what is depicted in FIGS. 6-11 , and wherein the sensor islocated at the distal end of the introducer handle.

FIG. 13 depicts an enlarged view of the circled portion of FIG. 12 .

FIG. 14 depicts the catheter and introducer also shown in FIG. 12 , butwith the catheter inserted more distally in the introducer, such thatthe ring electrodes at the distal end of the catheter shaft have allexited the distal end of the introducer shaft.

FIG. 15 is a fragmentary, isometric view of a distal end of anintroducer with the distal end of a catheter projecting from it, andwherein sensors are depicted in phantom embedded in the sidewall at adistal end of the introducer.

FIG. 16 is most similar to FIG. 15 , but depicts a sensor embedded inthe catheter shaft just proximal to the most proximal ring electrode.

FIG. 17 is a fragmentary view showing the distal end of an introducerhaving a sensor/detector projecting distally from a distal surface ofthe introducer and placed to sense or detect catheter electrodes passingby it as those electrodes exit from, or enter into, the introducer.

FIG. 18 is a fragmentary, isometric view that schematically depicts anintroducer shaft having a first element embedded in its inner sidewalland a catheter shaft having a complementary element embedded in itsouter sidewall, such that the first element and the second element passnear each other as the catheter moves relative to the introducer.

FIG. 19 schematically depicts the inner wall of an introducer havingmarker bands or stripes on it, and a catheter passing by the markerbands or stripes, the catheter having a sensor embedded in its outersidewall.

FIG. 20 is similar to FIG. 19 , but depicts a catheter having multiplesensors embedded in its sidewall to quickly detect a direction of motionof the catheter relative to the introducer.

FIG. 21 is a fragmentary, isometric view of the distal end of anoff-the-shelf catheter and a stencil hovering above the surface of thecatheter, the stencil being used to apply marker bands to the outersurface of the catheter.

FIG. 22 depicts a distal end of an off-the-shelf catheter passingthrough an introducer (shown in phantom), and depicts an ancillarydevice hovering above the catheter shaft, the ancillary device beingadapted to apply or ‘paint’ marker bands onto the catheter.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, in which like reference numerals refer tothe same or similar features in the various views, FIG. 1 illustratesone embodiment of a system 10 for navigating a medical device within abody 12. In the illustrated embodiment, the medical device comprises acatheter 14 that is shown schematically entering a heart that has beenexploded away from the body 12. The catheter 14, in this embodiment, isdepicted as an irrigated radiofrequency (RF) ablation catheter for usein the treatment of cardiac tissue 16 in the body 12. It should beunderstood, however, that the system 10 may find application inconnection with a wide variety of medical devices used within the body12 for diagnosis or treatment. For example, the system 10 may be used tonavigate an electrophysiological mapping catheter, an intracardiacechocardiography (ICE) catheter, or an ablation catheter using adifferent type of ablation energy (e.g., cryoablation, ultrasound,etc.). Further, it should be understood that the system 10 may be usedto navigate medical devices used in the diagnosis or treatment ofportions of the body 12 other than cardiac tissue 16.

Referring still to FIG. 1 , the ablation catheter 14 is connected to afluid source 18 for delivering a biocompatible irrigation fluid such assaline through a pump 20, which may comprise, for example, a fixed rateroller pump or variable volume syringe pump with a gravity feed supplyfrom fluid source 18 as shown. The catheter 14 is also electricallyconnected to an ablation generator 22 for delivery of RF energy. Thecatheter 14 may include a handle 24; a cable connector or interface 26at a proximal end of the handle 24; and a shaft 28 having a proximal end30, a distal end 32, and one or more electrodes 34. The connector 26provides mechanical, fluid, and electrical connections for conduits orcables extending from the pump 20 and the ablation generator 22. Thecatheter 14 may also include other conventional components notillustrated herein such as a temperature sensor, additional electrodes,and corresponding conductors or leads.

The handle 24 provides a location for the physician to hold the catheter14 and may further provide means for steering or guiding the shaft 28within the body 12. For example, the handle 24 may include means tochange the length of one or more pull wires extending through thecatheter 14 from the handle 24 to the distal end 32 of shaft 28. Theconstruction of the handle 24 may vary.

The shaft 28 may be made from conventional materials such aspolyurethane and may define one or more lumens configured to houseand/or transport electrical conductors, fluids, or surgical tools. Theshaft 28 may be introduced into a blood vessel or other structure withinthe body 12 through a conventional introducer (see, for example, FIGS. 2and 3 ). The shaft 28 may then be steered or guided through the body 12to a desired location such as the tissue 16 using guide wires or pullwires or other means known in the art including remote control guidancesystems. The shaft 28 may also permit transport, delivery, and/orremoval of fluids (including irrigation fluids and bodily fluids),medicines, and/or surgical tools or instruments.

The system 10 may include an electric-field-based positioning system 36,a magnetic-field-based positioning system 38, a display 40, and anelectronic control unit (ECU) 42. Each of the exemplary systemcomponents is described further below.

The electric-field-based positioning system 36 is provided to determinethe position and orientation of the catheter 14 and similar deviceswithin the body 12. The system 36 may comprise, for example, the ENSITENAVX system sold by St. Jude Medical, Inc. of St. Paul, Minn., anddescribed in, for example, U.S. Pat. No. 7,263,397 titled “Method andApparatus for Catheter Navigation and Location Mapping in the Heart,”the entire disclosure of which is hereby incorporated by reference asthough fully set forth herein. The system 36 operates based upon theprinciple that when low amplitude electrical signals are passed throughthe thorax, the body 12 acts as a voltage divider (or potentiometer orrheostat) such that the electrical potential or field strength measuredat one or more electrodes 34 on the catheter 14 may be used to determinethe position of the electrodes, and, therefore, of the catheter 14,relative to a pair of external patch electrodes using Ohm's law and therelative location of a reference electrode (e.g., in the coronarysinus).

In the configuration shown in FIG. 1 , the electric-field-basedpositioning system 36 further includes three pairs of patch electrodes44, which are provided to generate electrical signals used indetermining the position of the catheter 14 within a three-dimensionalcoordinate system 46. The electrodes 44 may also be used to generate EPdata regarding the tissue 16. To create axes-specific electric fieldswithin body 12, the patch electrodes are placed on opposed surfaces ofthe body 12 (e.g., chest and back, left and right sides of the thorax,and neck and leg) and form generally orthogonal x, y, and z axes. Areference electrode/patch (not shown) is typically placed near thestomach and provides a reference value and acts as the origin of thecoordinate system 46 for the navigation system.

In accordance with this exemplary system 36 as depicted in FIG. 1 , thepatch electrodes include right side patch 44X1, left side patch 44X2,neck patch 44Y1, leg patch 44Y2, chest patch 44Z1, and back patch 44Z2;and each patch electrode is connected to a switch 48 (e.g., a multiplexswitch) and a signal generator 50. The patch electrodes 44X1, 44X2 areplaced along a first (x) axis; the patch electrodes 44Y1, 44Y2 areplaced along a second (y) axis, and the patch electrodes 44Z1, 44Z2 areplaced along a third (z) axis. Sinusoidal currents are driven througheach pair of patch electrodes, and voltage measurements for one or moreposition sensors (e.g., ring electrodes 34 or a tip electrode locatednear the distal end 32 of catheter shaft 28) associated with thecatheter 14 are obtained. The measured voltages are a function of thedistance of the position sensors from the patch electrodes. The measuredvoltages are compared to the potential at the reference electrode and aposition of the position sensors within the coordinate system 46 of thenavigation system is determined.

The magnetic-field-based positioning system 38 in this exemplaryembodiment employs magnetic fields to detect the position andorientation of the catheter 14 within the body 12. The system 38 mayinclude the GMPS system made available by MediGuide, Ltd. and generallyshown and described in, for example, U.S. Pat. No. 7,386,339 titled“Medical Imaging and Navigation System,” the entire disclosure of whichis hereby incorporated by reference as though fully set forth herein. Insuch a system, a magnetic field generator 52 may be employed havingthree orthogonally arranged coils (not shown) to create a magnetic fieldwithin the body 12 and to control the strength, orientation, andfrequency of the field. The magnetic field generator 52 may be locatedabove or below the patient (e.g., under a patient table) or in anotherappropriate location. Magnetic fields are generated by the coils andcurrent or voltage measurements for one or more position sensors (notshown) associated with the catheter 14 are obtained. The measuredcurrents or voltages are proportional to the distance of the sensorsfrom the coils, thereby allowing determination of a position of thesensors within a coordinate system 54 of system 38.

The display 40 is provided to convey information to a physician toassist in diagnosis and treatment. The display 40 may comprise one ormore conventional computer monitors or other display devices. Thedisplay 40 may present a graphical user interface (GUI) to thephysician. The GUI may include a variety of information including, forexample, an image of the geometry of the tissue 16, electrophysiologydata associated with the tissue 16, graphs illustrating voltage levelsover time for various electrodes 34, and images of the catheter 14 andother medical devices and related information indicative of the positionof the catheter 14 and other devices relative to the tissue 16.

The ECU 42 provides a means for controlling the operation of variouscomponents of the system 10, including the catheter 14, the ablationgenerator 22, and the switch 48 of the electric-field-based positioningsystem 36, and magnetic generator 52 of the magnetic-field-basedpositioning system 38. For example, the ECU 42 may be configured throughappropriate software to provide control signals to switch 48 and therebysequentially couple pairs of patch electrodes 44 to the signal generator50. Excitation of each pair of electrodes 44 generates anelectromagnetic field within the body 12 and within an area of interestsuch as the heart. The ECU 42 may also provide a means for determiningthe geometry of the tissue 16, electrophysiology characteristics of thetissue 16, and the position and orientation of the catheter 14 relativeto tissue 16 and the body 12. The ECU 42 also provides a means forgenerating display signals used to control the display 40. The depictedECU 42 represents any processing arrangement such as, for example,single device processors, multiple device processors (e.g.,co-processors, master/slave processors, etc.), distributed processingacross multiple components/systems, system on chip (SOC) devices, or thelike.

As the catheter 14 moves within the body 12, and within the electricfield generated by the electric-field-based positioning system 36, thevoltage readings from the electrodes 34 change, thereby indicating thelocation of catheter 14 within the electric field and within thecoordinate system 46 established by the system 36. The ring electrodes34 communicate position signals to ECU 42 through a conventionalinterface (not shown). In order to avoid introducing undesirable shiftor drift into the determined catheter position and orientation basedupon readings obtained by the electric-field based positioning system36, it can be important to know when the catheter electrodes 34 areinside the introducer. In particular, if the catheter electrodes 34 arelocated inside the introducer, the data coming off of those shieldedelectrodes may be degraded/compromised.

FIG. 2 depicts a steerable introducer 56 having a sensor 58 (e.g., aproximity sensor) affixed to a cap 60 of a hemostasis valve 62. Althoughthe proximity sensor 58 is depicted as an external component, it couldbe internal to the handle 64. Also visible in FIG. 2 is a Tuohy-Borstside arm assembly 66, including a Tuohy-Borst adapter 68 and a stopcock70. A steering actuator 72 is shown at the distal end of the handle 64,and a strain relief 74 (or retaining nut) is shown just distal to thesteering actuator 72. An introducer shaft 76 extends rightward in FIG. 2from the strain relief 74 to an atraumatic tip 78 at the distal end ofthe shaft. An electrode 80 is also depicted in FIG. 2 near theatraumatic tip 78. A connector 82 is available to electrically connectthe sensor 58 to, for example, the ECU 42 (FIG. 1 ). Finally, thesteerable introducer 56 depicted in FIG. 2 may include on-boardinformation storage 84 (e.g., an EEPROM or other memory device) mountedinside the handle housing. The introducer depicted in FIG. 2 is similarto the AGILIS ES steerable introducer manufactured by St. Jude Medical,Inc., of St. Paul, Minn., and is depicted as a representative example ofan introducer or other enveloping device in which the principlesdescribed herein may be implemented.

FIG. 3 depicts a fixed-curve introducer 86. The fixed-curve introducerhas a hemostasis valve 62′ at its proximal end. The hemostasis valveincludes a cap 60′ that includes an annular groove 88 that is configuredto accept the gripping arms 90 of a clip-on sensor 92 such as the onedepicted in, for example, FIG. 4 . The clip-on sensor depicted in FIG. 4includes a sensor head 94 and a mounting clip 96 comprising the grippingarms 90 shown riding in the annular groove 88 in the hemostasis valvecap 60′ of FIG. 3 . An electrical connector is depicted in FIG. 3 forelectrically connecting the sensor 92 to a navigation system 10 such asthe one depicted in FIG. 1 . The fixed-curve introducer, as shown inFIG. 3 , also includes a Tuohy-Borst side arm assembly 66, including aTuohy-Borst adapter 68 and a stopcock 70. The fixed-curve introducerdepicted in FIG. 3 is similar to a SWARTZ BRAIDED introducer sold by St.Jude Medical, Inc., and is depicted as another representative example ofan introducer or other enveloping device in which the principlesdescribed herein may be implemented. An atraumatic tip 78′ is depictedat the distal end of the introducer shaft 76′. The clip-on sensor 92 isa separate, re-sterilizable device that could be attached to theproximal end of the introducer 86.

FIG. 5 depicts a catheter 14′ having a plurality of electrodes 34 for avariety of diagnostic and therapeutic purposes including, for example,electrophysiological studies, catheter identification and location,pacing, and cardiac mapping and ablation. Although the catheter 14′, forpurposes of this invention, could be a therapy or diagnostic catheter,the catheter depicted in FIG. 5 is most similar to the SAFIRE ablationcatheter manufactured by St. Jude Medical, Inc., and is depicted as arepresentative example of a catheter or other advanceable intrabodydevice in which the principles described herein may be implemented.

In FIG. 5 , a marker band 98 is shown near the proximal end of thecatheter shaft 28′. The marker band could extend around the entirecircumference of the catheter shaft, or it could be one or more arcuatepieces rather than a complete ring. The marker band 98 could also be anembedded spot or puck or other recessed, detectable component (e.g.,lines or tick marks like the transverse markings on a tape measure). Themarker band 98 could be molded into or applied to the surface of thecatheter shaft 28; and, the marker band could be added to the cathetershaft during assembly of the catheter, or it could be added at a latertime, including just prior to a procedure in an electrophysiology (EP)lab. The application of marker bands on catheter shafts, “on the fly” inan EP lab is discussed further below in connection with FIGS. 21 and 22.

Preferably, the marker band or bands 98 on the catheter shaft are flushor nearly flush with the outer surface of the catheter shaft 28′ so thatthey may fit through the seal in the hemostasis valve (62 or 62′ or 62″)of the steerable or fixed-curve introducer 56, 86, respectively.However, an enlarged marker band (not shown) that does not fit throughthe hemostasis valve could be used if the physician or clinician onlywanted to know when the most proximal ring electrode exits the distalend of the introducer. At that point, the enlarged marker band couldactually come into physical contact with the proximal side of thehemostasis valve and, alternatively, be simultaneously sensed by thesensor 58 and reported to the navigation system 10. Similar to what wasdescribed in connection with the introducer shown in FIG. 2 , thecatheter depicted in FIG. 5 may also include on-board storage 84′ suchas an EEPROM, shown in FIG. 5 as being mounted within the catheterhandle housing. The EEPROM could store, for example, information aboutthe location of the marker band, including the distance from the markerband to the tip electrode along the catheter shaft, and/or the distancefrom the marker band to the most-proximal ring electrode, and/or thedistance from the marker band to each of a plurality of ring electrodeson the catheter shaft. When the catheter is connected via the electricalconnector 26 to the navigation system depicted in FIG. 1 , thenavigation system could thereby learn about the marker band and itsplacement along the catheter shaft. Finally, a light 100 (e.g., an LED)may be present on the catheter handle 24′ as explained further below.

FIG. 6 depicts a catheter assembly 102, comprising the catheter 14′shown in FIG. 5 inserted into the steerable introducer 56 shown in FIG.2 . When the catheter shaft 28′ is inserted down the throat of theintroducer as shown in FIG. 6 , the distal end of the catheter shaftprotrudes from the sheath distal end. In this particular embodiment,when the most proximal catheter electrode exits the distal end of thesheath, a marker band is detected by the proximity sensor 58, and theindicator light 100 lights up. Alternatively, the indicator light 100could be red until the marker band 98 is detected by the proximitysensor and then go out or turn green. Other feedback may be used in lieuof or in addition to visual feedback, such as audible, tactile (e.g.,vibratory) and/or other perceivable feedback. The fact that the mostproximal catheter electrode has exited from the distal end of theintroducer shaft 76 may also be reported through the connector 82 to thenavigation system 10 depicted in FIG. 1 . The navigation system reliesupon knowing that the ring electrodes and tip electrode 34 are notwithin the introducer shaft 76. If one or more of the ring electrodes,for example, are retracted into the introducer shaft 76, the navigationsystem receives degraded or compromised data and may miscalculate or becompletely unable to determine where the catheter is located within, forexample, an anatomical model of the patient's heart.

FIG. 7 is an enlarged view of the circled region of FIG. 6 , depicting amost-proximal catheter electrode 104 adjacent to the distal end 106 ofthe introducer shaft 76.

FIGS. 8 and 9 schematically depict the steerable introducer 56 andcatheter 14′ shown in, for example, FIG. 6 . As shown in FIG. 8 , themarker band 98 on the catheter 14′ is detected by the proximity sensor58 on the introducer 56 as the most-proximal ring electrode 104 exitsfrom the distal end of the introducer 106. The compatibility of a givenintroducer with a given catheter is determined by ensuring that thedistance from the proximity sensor 58 to the distal end 106 of theintroducer 56 is the same as the distance from the marker band 98 to themost-proximal ring electrode 104 of the catheter 14′. These twodistances are both represented as ‘D’ in FIGS. 8 and 9 . In FIG. 9 , asrepresented by the arrow 108, the catheter 14′ has been moved proximally(i.e., leftward in this figure), thereby retracting the most proximalring electrode 104 into the introducer shaft 76. At that point, thenavigation system would no longer receive accurate information from themost proximal ring electrode 104. At that point, the navigation systemcould be configured to ignore the data being collected from the mostproximal electrode 104, or ignore the data being collected from all ofthe electrodes 34, depending upon the desired settings for a particularphysician.

The embodiments shown in FIGS. 5-9 actively measure or indicate onlywhen the most proximal electrode 104 enters the introducer shaft 76. Itmay, however, be desirable to know when each of a plurality ofelectrodes on the catheter enters into or exits from the distal end ofthe introducer. A couple of configurations capable of supplying thathigher resolution information are described next.

FIG. 10 is similar to FIG. 6 , but depicts a catheter 14″ having aplurality of marker bands 98′ on the catheter shaft portion closest tothe catheter handle 24″. In this particular configuration, there is aseparate marker band for each ring electrode and a separate marker bandfor the tip electrode. In the configuration and relative placement ofthe catheter 14″ and introducer 56 shown in FIG. 10 , the tip electrode110 is right at the distal 106 end of the introducer shaft 76. Thus, themarker band 112 for the tip electrode 110 is shown just passing thesensor 58. In FIG. 10 , the distal portion of the introducer shaft wallis broken away to reveal the fact that the three ring electrodes 34 areinside the sheath. The marker bands corresponding to these electrodesare, therefore, still proximal to the sensor 58. That is, the markerbands corresponding to the ring electrodes have not yet passed under thesensor that is attached to the proximal side of the cap 60 on thehemostasis valve 62.

FIG. 11 is similar to FIGS. 8 and 9 and schematically depicts a markerband and electrode configuration that is also depicted in FIG. 10 . Asclearly shown in FIG. 11 , there is a separate marker band for each ofthe three electrodes and a single marker band for the tip electrode.Each marker band is separated from its ring or tip electrode by adistance D, which corresponds to the internal length of the introducer.This configuration is, therefore, able to provide information to thenavigation system and thus to the clinician when each of the ringelectrodes is retracted into the introducer and thus stops supplyingreliable location data or patient information to the navigation system.As shown in FIG. 10 , the catheter handle 24″ may include a LED 100 foreach of the ring electrodes 34 and an LED 114 for the tip electrode 110.As previously discussed, these indicator lights or LEDs may be visualindicators to the physician about how many and which electrodes arecurrently providing reliable data to the navigation system 10.

FIGS. 12-14 depict another embodiment. In this particular embodiment,the sensor 58′ (see FIG. 13 ) has been moved from the hemostasis valve62″ to the strain relief 74′ at the distal end of the steerableintroducer handle 64′. This may be clearly seen in FIG. 13 which is anenlarged view of the circled portion of FIG. 12 . As shown in FIG. 13 ,the sensor 58′ (e.g., a proximity sensor) is embedded in a sidewalladjacent to the inner surface of the introducer shaft and positioned tosense the passing of marker bands on the catheter shaft. In FIGS. 12 and13 , a portion of the strain relief member 74′ is broken away so thatyou can see not only the proximity sensor 58′, but also the marker bandson the catheter shaft 28″. Similarly, a portion of the introducersidewall is broken away near the distal end 106 of the introducer sothat it is possible to see that the ring electrodes 34 at the distal endof the catheter shaft are inside the introducer and the tip electrode110 is just exiting the distal end 106 of the introducer shaft 76. Themarker band 112′ corresponding to the tip electrode is, therefore, justpassing by the proximity sensor 58′ embedded in the strain relief member74′. In order to transfer signals from the proximity sensor to thenavigation system in this embodiment, an electrical lead 116 wouldextend to the strain relief member 74′ (e.g., inside of the steerableintroducer handle). FIG. 14 is similar to FIG. 12 ; however, in FIG. 14the catheter has been inserted deeper into the introducer. At thispoint, the tip electrode 110 and all three ring electrodes 34 at thedistal end of the catheter are extended from the distal end of theintroducer. The distance D1 is the distance from the most proximal ringelectrode to the distal end of the introducer, and is also the distancefrom the most proximal marker band to the proximity sensor mounted inthe strain relief member. Again, the catheter handle may include aseries of lights to provide visual feedback, and/or audible, tactile orother feedback to a physician as to a number of electrodes providingreliable location data to a navigation system at any point in time.

As described herein, a catheter shaft may be equipped or otherwiseconfigured to accommodate the detection of its own electrodes traversinga distal opening on a partnering introducer. In one embodiment, acatheter, such as catheter 14′, includes a catheter shaft 28′. Thecatheter shaft 28′ may include one or more electrodes, such as ringelectrodes 34, at its distal portion. The catheter shaft 28′ may furtherinclude at least one detectable marker 98 positioned proximal to theelectrode(s) 34 at the distal portion of the shaft 28′. The detectablemarker 98 may be positioned a predetermined distance, such as distance Dof FIGS. 8 and 9 , from a most proximal electrode 104 of theelectrode(s) 34. In one embodiment, the predetermined distance D maycorrespond to a distance from a distal opening at the tip 78 of aninteroperable introducer, such as introducers 56/86, to a markerdetector (e.g., sensors 58, 58′, sensor head 94, etc.) positioned alongthe introducer proximal to its distal opening. In another embodiment,one or more additional detectable markers 98′ may each be positionedproximal to a plurality of the electrodes 34 at the distal portion ofthe shaft 28′, where each of the detectable markers 98′ is positioned apredetermined distance D from a respective one of the plurality theelectrodes 34.

Since it may be critical to be able to discern which electrodes and howmany electrodes are extending past the distal end of the introducer atany particular time, it can be advantageous to sense the location of theelectrodes from the distal end of the introducer. In the configurationdepicted in FIG. 6 , the sensed marker bands are displaced a substantialdistance from the electrodes. In the configurations depicted in, forexample, FIGS. 12-14 , the sensed marker bands have been moved closer tothe distal end of the introducer. In the embodiments depicted in FIGS.15-18 , the electrodes are being detected right at the distal end of theintroducer.

In FIG. 15 , the distal portion of the catheter 14′″ is shown extendingslightly past the distal end 106″ of the introducer 56′. Proximitysensors 58″ at the distal end of the introducer 56′ are shown in dashedlines. In this configuration, the sensors may be, for example,inductive-type sensor coils. In order to provide corresponding data tothe navigation system 10, a lead wire (not shown) would preferably runin the sidewall of the introducer 56′ from the sensors 58″ to theconnector 82 at the proximal end of the introducer. Providing lead wiresin the sidewall of an introducer can create some manufacturingchallenges and may undesirably reduce the inside diameter of theintroducer that is available for catheters.

In the embodiments depicted in FIG. 16 , the proximity sensor 58′″ hasbeen moved to a location on the shaft of the catheter 14″″ just proximalof the most-proximal ring electrode 104. This proximity sensor 58′″could be configured to detect when it passes the coils or rings 118mounted in the distal end 106′″ of the introducer 56″.

In the embodiment of FIG. 17 , a sensor/detector 58″″ projects from thedistal surface 120 of the introducer shaft 76″. The sensor/detector 58″″is configured to detect passage of the ring electrodes 34 and tipelectrode 110 from the distal end of the introducer. This data would bereported back to the navigation system 10 through the electrical lead116′.

FIG. 18 is a fragmentary, schematic view of a distal portion of anintroducer shaft 76′″ and a distal portion of a catheter shaft 28′″. Afirst element 122 is depicted embedded in the inner wall of theintroducer shaft 76′″ adjacent the distal end surface of the introducershaft. A second element 124 is shown embedded in the outer surface ofthe catheter shaft 28′″. As these two elements pass each other,information could be communicated back to the navigation system 10concerning the location of catheter shaft electrodes vis-à-vis the endof the introducer. One of these elements 122, 124 would be a sensedelement and the other one would be a sensor. Thus, an electrical lead116″ would run from at least one of these elements back to thenavigation system 10. In FIG. 18 , the lead 116″ is shown connected tothe second element 124.

FIG. 19 schematically depicts a section of the inner wall of anintroducer shaft above a fragmentary section of a catheter shaft 28″.The inner wall 126 of the introducer is shown with a plurality of markerbands or stripes 128 on it, and the catheter shaft is depicted with asingle sensor 130 arranged to pass closely adjacent to the bands 128 onthe inner wall 126 of the introducer. The bands or stripes 128 on theinner wall of the introducer could be located anywhere on the length ofthe introducer. In one configuration, each band has a different colorand the sensor 130 is able to detect color. The sensor is thus able toreport back to the navigation system 10 which band it is closest to,which would allow the navigation system to determine which electrode orelectrodes must be extending from the distal end of the introducer, ifany. The sensor may also be able to detect a direction of travel of thecatheter shaft relative to the introducer after the sensor passes atleast two bands.

FIG. 20 is similar to FIG. 19 , but depicts a catheter shaft 28′″″having a plurality of sensors 130 mounted and configured to read theplurality of marker bands 128 on the inner wall 126′ of an introducer.This two-sensor configuration would be able to provide both location anddirectionality information to a navigation system.

FIG. 21 is an isometric, fragmentary view of the distal portion of anoff-the-shelf catheter 132. In this figure, a stencil 134 is shownexploded away from the outer surface of the catheter 132. The stencilcould be used to apply marker band material to create marker bands onthe outer surface of an off-the-shelf catheter while in, for example,the EP lab. This embodiment contemplates having a plurality of stencils,possibly one stencil for each of a variety of different types or brandsof catheters. Using an appropriate stencil, a physician or techniciancould ‘paint on’ or ‘apply’ marker bands to the catheter of his or herchoice, thereby also permitting the navigation system to determine whenthe catheter electrodes are outside of the sheath and available forreporting accurate location information.

FIG. 22 is a fragmentary, isometric view of an off-the-shelf catheter132 mounted in an introducer 56 (shown schematically in phantom in thisfigure). As clearly depicted in FIG. 22 , the catheter 132 has threering electrodes 34 at its distal end. The most distal ring electrode isshown in FIG. 22 about to exit from the distal end of the introducer 56.Three marker bands 134′, corresponding to the three ring electrodes 34,are also depicted in FIG. 22 . The most distal marker band is shownabout to pass under a proximity sensor 58 on the introducer since themost distal of ring electrodes 34 is about to exit the introducer 56.Hovering above the marker bands 134′ is an ancillary device 136 that wasused to put the marker bands on the catheter shaft. In particular, thisreusable, ancillary device 136 may temporarily and removably clamp on oraround a catheter shaft to apply marker bands to an off-the-shelfcatheter. The ancillary device 136 could be clamped around the cathetershaft and then rotated about the catheter shaft's longitudinal axis 138in order to draw arcuate or circumferential marker bands on the shaft.Once the bands have been placed on the shaft, the ancillary device wouldbe removed before inserting the catheter into the introducer.

A system 10 and method for navigating a medical device within a body 12in accordance with the present teachings enables consistent correctionof errors in position measurements due to shift or drift in patientimpedance levels. Further, the system 10 and method do not require theuse of an additional reference catheter and the resulting increases inprocedure time and risks.

Embodiments are described herein of various apparatuses, systems, and/ormethods. Numerous specific details are set forth to provide a thoroughunderstanding of the overall structure, function, manufacture, and useof the embodiments as described in the specification and illustrated inthe accompanying drawings. It will be understood by those skilled in theart, however, that the embodiments may be practiced without suchspecific details. In other instances, well-known operations, components,and elements have not been described in detail so as not to obscure theembodiments described in the specification. Those of ordinary skill inthe art will understand that the embodiments described and illustratedherein are non-limiting examples, and thus it can be appreciated thatthe specific structural and functional details disclosed herein may berepresentative and do not necessarily limit the scope of allembodiments.

Reference throughout the specification to “various embodiments,” “someembodiments,” “one embodiment,” or “an embodiment,” or the like, meansthat a particular feature, structure, or characteristic described inconnection with the embodiment(s) is included in at least oneembodiment. Thus, appearances of the phrases “in various embodiments,”“in some embodiments,” “in one embodiment,” or “in an embodiment,” orthe like, in places throughout the specification, are not necessarilyall referring to the same embodiment. Furthermore, the particularfeatures, structures, or characteristics may be combined in any suitablemanner in one or more embodiments. Thus, the particular features,structures, or characteristics illustrated or described in connectionwith one embodiment may be combined, in whole or in part, with thefeatures, structures, or characteristics of one or more otherembodiments without limitation given that such combination is notillogical or non-functional.

It will be appreciated that the terms “proximal” and “distal” may beused throughout the specification with reference to a clinicianmanipulating one end of an instrument used to treat a patient. The term“proximal” refers to the portion of the instrument closest to theclinician and the term “distal” refers to the portion located furthestfrom the clinician. It will be further appreciated that for concisenessand clarity, spatial or directional terms such as “vertical,”“horizontal,” “up,” “down,” “clockwise,” and “counterclockwise” may beused herein with respect to the illustrated embodiments. However,medical instruments may be used in many orientations and positions, andthese terms are not intended to be limiting and absolute. Joinderreferences (e.g., attached, coupled, connected, and the like) are to beconstrued broadly and may include intermediate members between aconnection of elements and relative movement between elements. As such,joinder references do not necessarily infer that two elements aredirectly connected and in fixed relation to each other. Changes indetail or structure may be made without departing from the spirit of theinvention as defined in the appended claims.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

What is claimed is:
 1. A system comprising: a catheter comprising aplurality of electrodes on a catheter distal portion; and an introducercomprising a proximity sensor on an introducer distal portion; whereinthe catheter is configured to pass through the introducer; and whereinthe proximity sensor is configured to detect passage of at least one ofthe plurality of electrodes from the introducer distal portion, whereinat least one of the plurality of electrodes is configured to indicatelocation of the catheter within an electric field-based positioningsystem.
 2. The system of claim 1, wherein the proximity sensor comprisesa plurality of coils.
 3. The system of claim 1, wherein the introducerfurther comprises a lead wire coupled to the proximity sensor.
 4. Thesystem of claim 3, wherein the lead wire is disposed within a sidewallof the introducer.
 5. The system of claim 1, further comprising anelectronic control unit (ECU) electrically coupled to the proximitysensor.
 6. The system of claim 5, wherein the ECU is configured tomonitor a signal originating from the proximity sensor to determine whenat least one of the plurality of electrodes passes the proximity sensor.7. The system of claim 5, wherein the ECU is configured to analyze asignal originating from the proximity sensor to determine whether atleast one of the plurality of catheter electrodes is within theintroducer.
 8. The system of claim 5, wherein the ECU is configured toanalyze a signal originating from the proximity sensor to determinewhether a particular one of the plurality of catheter electrodes iswithin the introducer.
 9. The system of claim 5, wherein the ECU isfurther configured to indicate when one of the plurality of electrodesexits or enters the introducer.
 10. The system of claim 5, wherein thecatheter further comprises a memory device adapted to store dimensioninformation about the catheter.
 11. The system of claim 10, wherein thememory device is an EEPROM.
 12. A system comprising: a cathetercomprising a proximity sensor located on a shaft of the catheter and aplurality of electrodes on a catheter distal portion; and an introducercomprising a plurality of rings mounted in an introducer distal portion;wherein the catheter is configured to pass through the introducer; andwherein the proximity sensor is configured to detect passage of theplurality of rings mounted in the introducer distal portion.
 13. Thesystem of claim 12, wherein the proximity sensor is disposed proximal ofthe plurality of electrodes.
 14. The system of claim 12, wherein atleast one of the plurality of electrodes is configured to indicatelocation of the catheter within an electric field-based positioningsystem.
 15. The system of claim 12, wherein each of the plurality ofrings comprises an inductive coil.
 16. The system of claim 12, furthercomprising an electronic control unit (ECU) electrically coupled to theproximity sensor.
 17. The system of claim 16, wherein the ECU isconfigured to monitor a signal originating from the proximity sensor todetermine when the proximity sensor passes at least one of the pluralityof rings.
 18. The system of claim 16, wherein the catheter furthercomprises a memory device adapted to store dimension information aboutthe catheter.
 19. The system of claim 18, wherein the memory device isan EEPROM.